The first time with the Titan Suit so get yourself acquainted with the controls, the way you move and how far your punches reach. You'll have to knock through several walls here where after some grunts will immediately attack you by jumping on your mech and smashing it. Try to avoid this by hitting them with your punches before they can jump you, but if they manage to get on shaking them off isn't that much trouble. Alternatively, another effective strategy is to exit the Titan Suit, get rid of the grunts manually, and then re-enter the suit again.
Smash some more walls and grunts until you find a big stone cube; push this one against the wall on the left and use it to jump over there. There's a rapid gunner at the end of the corridor to the right and while you can tank the damage with your mech, just hop out and shoot it with the Blaster while it reloads. Next is another block you need to move, followed by two more rapid gunners. Take these out as well and use the Titan Suit to get to another block you need to move around.
Continue on until you reach a pillar; knock it down to create a bridge and then get rid of the fourth gunner a little up ahead. There's a smaller stone block next to that one, pick it up and go back a little where you can use it to destroy another pillar to create another bridge.